Tom Sawyer's and Huckleberry Finn's adventures are legendary, but what about the story you haven't heard? In 1860, eleven-year-old Becky Thatcher is the new girl in town, determined to have adventures like she promised her brother Jon before he died. With her Mama frozen in grief and her Daddy busy as town judge, Becky spends much of her time on her own, getting into mischief. Before long, she joins the boys at school in a bet to steal from the Widow Douglas, and Becky convinces her new best friend, Amy Lawrence, to join her.

But the theft doesn't go as planned, and Widow Douglas ends up being unfairly accused of grave robbing as a result. So Becky concocts a plan to clear the Widow's name. If she pulls it off, she might just get her Mama to notice her again, as well as fulfill her promise to Jon in a most unexpected way. That is, if that tattletale Tom Sawyer will quit following her around.